1. Field of the Invention
Apparatuses and methods consistent with the present invention relates to an encoder/decoder (CODEC), and more particularly, to compressing/decompressing data, in which lossless compression is applied to a raw data transfer mode in order to decompress data into high-quality data in a CODEC system.
2. Description of the Related Art
The H.264 CODEC innovatively improves compression rate and display quality using more varied and complex techniques than related art video compression standards. For this reason, the H.264 CODEC, which is used as a substitute for related art video compression standards, is in the limelight as an application technique for digital multimedia broadcasting (DMB) or digital versatile discs (DVDs).
In the H.264 CODEC, video data is compressed by performing a prediction process on sample data in block units in order to obtain a prediction block composed of prediction samples, and transforming and quantizing a residue block obtained from prediction blocks.
Two methods are used for prediction: intraprediction and interprediction. Interprediction performs prediction by performing motion compensation/estimation with reference to a reference picture that has passed through an encoding/decoding process and deblocking filtering. Intraprediction performs prediction in a current picture using data of neighboring blocks that are already encoded. Video data compressed by passing through a prediction process and a transformation & quantization process is compressed again through an entropy coding process to become a bitstream conforming to the H.264 standard.
The H.264 CODEC improves video quality using intra pulse coded modulation (I_PCM) in which raw data of a specific macroblock is transferred without being compressed. However, a raw data transfer mode of the H.264 CODEC requires 3072 bits per macroblock in a 4:2:0 format. The raw data transfer mode, although providing best video quality, may not meet a threshold set by a user due to an excessive amount of bits used in mode decision and rate distortion optimization (RDO) or may not be selected in view of efficiency.